1. Field of the Invention
This invention relates to a one-way snap fastener, that is, a snap fastener which can be snapped closed but cannot be unsnapped without destroying it. Such fasteners are used, for instance, in attaching plastic strap bracelets to patients in a hospital. The purpose of such a bracelet is to identify the patient in a way which is reliable and cannot be defeated by its inadvertent or willful removal.
More specifically, this invention relates to a one-way snap fastener in which the head presents a plurality of barbs which spring out after they snap together and then tend to spring out further and lock even tighter upon attempts to unsnap the fastener.
2. Description of the Prior Art
The prior art is of course replete with snap fasteners of different descriptions. There are, however, examples of permanently locking fasteners or one-way fasteners pertinent to the present invention. For instance, U.S. Pat. 3,416,200, which issued Dec. 17, 1968 to Daddona, discloses a fastener wherein the stud has a solid head and the socket has an upwardly inclined annular strut which catches under the head after the snap installation. There is ample room in the socket opening to permit tilting of the head.
In U.S. Pat. No. 3,210,820, which issued Oct. 12, 1965 to J. H. Humiston, the head is split and squeezes together as it passes the neck of the socket.